| OZOBOT 1643368 · TMA951983 | EVOLLVE, INC. | 9 Electronics28 Toys | Registered | 2016 |
| Oasbit 2339349 | Owner not listed | 35 Advertising | Pending | 2024 |
| oyespet 2134909 · TMA1212064 | Shenzhen Oyes Technology Co. Ltd | 21 Housewares | Registered | 2023 |
| OSBTJKJ 2120420 · TMA1186419 | Shibing Tuji (Shenzhen) Technology Co. Ltd. | 11 Lighting | Registered | 2023 |
| OXEFIT 2113279 · TMA1202702 | OXEFIT INC. | 28 Toys | Registered | 2023 |
| OGEFOTED 2067543 · TMA1157442 | Yiwu Pinzhu E-commerce Co.Ltd. | 21 Housewares | Registered | 2022 |
| OXYPOD 2004449 · TMA1184661 | Pollogen Ltd. | 3 Cosmetics | Registered | 2023 |
| OUSFOT 1998382 · TMA1127067 | DongGuan Sogoode Computer System Co. Ltd | 11 Lighting | Registered | 2022 |
| OKFIT 1913799 · TMA1110235 | Go-Hard | 9 Electronics11 Lighting14 Jewellery+9 | Registered | 2021 |
| OKCUPID 1772794 · TMA1045923 | Humor Rainbow, Inc. | 41 Education | Registered | 2019 |
| OKCUPID 1768365 · TMA1045922 | Humor Rainbow, Inc. | 42 Science45 Legal | Registered | 2019 |
| OCUPATCH 1740878 · TMA1030843 | SENJU PHARMACEUTICAL CO., LTD. | 1 Chemicals5 Pharmaceuticals | Registered | 2019 |
| OxyPowder 1641488 · TMA916227 | Slante Holdings LLC | 5 Pharmaceuticals35 Advertising | Registered | 2015 |
| OSPT 1540218 · TMA884154 | Owner not shown | 9 Electronics39 Transport41 Education+1 | Registered | 2014 |
| OXYPHTHIRINE 1382360 · TMA816246 | an individual | 3 Cosmetics5 Pharmaceuticals | Registered | 2012 |
| OKAPED 1242762 · TMA705625 | Okanagan Pedorthics & Sports Bracing Inc. | 10 Medical35 Advertising40 Treatment+3 | Registered | 2008 |
| OKgift 1099763 · TMA580461 | an individual | 35 Advertising | Registered | 2003 |
| OXYBUTYN 0848549 · TMA495334 | Bausch Health, Canada Inc. | 5 Pharmaceuticals | Registered | 1998 |
| OXOPOTINE 0827715 · TMA519121 | an individual | 5 Pharmaceuticals | Registered | 1999 |
| OCUVITE 0694407 · TMA408499 | BAUSCH & LOMB INCORPORATED | 5 Pharmaceuticals | Registered | 1993 |
| OXYVET 0342992 · TMA183532 | Vétoquinol N.A. Inc. | 5 Pharmaceuticals | Registered | 1972 |
| Occipital 2310260 | an individual | 9 Electronics | Pending | 2024 |
| OSSEOFIT 2293279 | Owner not listed | 10 Medical | Pending | 2023 |
| OCIFTY 2266592 | BeiGene Switzerland GmbH | 5 Pharmaceuticals | Pending | 2023 |
| OXOBET 2139081 · design | an individual | 9 Electronics36 Finance38 Telecommunications+1 | Pending | 2021 |